Hologram displaying apparatus and method thereof

Abstract

In the present invention, by providing a hologram displaying apparatus including a light source configured to emit input light, a spatial light modulator configured to modulate the input light into diffracted light, and a plurality of noise filtering elements configured to remove optical noise components from the diffracted light modulated by the spatial light modulator, and display a hologram, an optical path of a light source for displaying the hologram can be drastically reduced while effectively performing spatial filtering.

What is claimed is: 
     
       1. A hologram displaying apparatus, comprising:
 a light source configured to emit input light; 
 a spatial light modulator configured to modulate the input light into diffracted light and including a plurality of pixel blocks; and 
 a plurality of noise filtering elements configured to remove optical noise components from the diffracted light modulated by the spatial light modulator, and display a hologram, 
 wherein each of the plurality of noise filtering elements corresponds to one of the plurality of pixel blocks, and comprises:
 a first lens corresponding to a pixel block and focusing the light diffracted by the pixel block; 
 a spatial filter for removing an optical noise component from the focused diffracted light; and 
 a second lens for transmitting noise filtered diffracted light of the focused diffracted light, 
 wherein both of the spatial filter and the second lens are disposed on a back focal plane of the first lens. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the first lens is in contact with the pixel block and each of the plurality of noise filtering elements further includes:
 a third lens disposed in parallel corresponding to the spatial filter, and displaying the hologram using the noise filtered diffracted light. 
 
     
     
       3. The apparatus of  claim 2 , wherein each of the first lens, the second lens, and the third lens includes a diffractive optical element or a refractive optical element. 
     
     
       4. The apparatus of  claim 3 , wherein the first lens includes a first hologram optical element, and blocks part of waves of the light diffracted by the pixel block in a specific direction. 
     
     
       5. The apparatus of  claim 4 , wherein the second lens includes a second hologram optical element, and blocks part of waves of the light diffracted by the pixel block in a specific direction. 
     
     
       6. The apparatus of  claim 5 , wherein
 the first hologram optical element is configured to block higher-order diffraction components beyond the second order diffraction component diffracted in a first direction of the light diffracted by the pixel block, and 
 the second hologram optical element is configured to block higher-order diffraction components beyond the second order diffraction component focused in a second direction of the focused diffracted light. 
 
     
     
       7. The apparatus of  claim 6 , wherein each of the first hologram optical element and the second hologram optical element is composed of a volume diffractive optical element. 
     
     
       8. The apparatus of  claim 3 , wherein
 the first lens and the third lens have a first focal length, and 
 a sum of a size of the second lens and a size of the spatial filter is equal to a size of the pixel block. 
 
     
     
       9. The apparatus of  claim 8 , wherein a width of the light diffracted from each pixel block is twice a second focal length of the second lens. 
     
     
       10. The apparatus of  claim 9 , further comprising:
 an upper partition wall for blocking light diffracted from each pixel block into an upper region of the second lens, and 
 a lower partition wall for blocking light diffracted from each pixel block into a lower region of the spatial filter. 
 
     
     
       11. The apparatus of  claim 2 , wherein the spatial filter is a single sideband filter for blocking a direct current (DC) component of the focused diffracted light and a conjugated component of the focused diffracted light from which the DC component is removed. 
     
     
       12. A hologram displaying apparatus, comprising a spatial light modulator, a first lens module, a second lens module, and a third lens module, wherein
 the first lens module to the third lens module are convex lens modules, 
 the first lens module is located in contact with an input image plane of the spatial light modulator and applies focusing power on the light wave modulated in the spatial light modulator to prevent the modulated light wave from diverging, 
 the second lens module is located on a rear focal plane of the first lens module and projects the light wave to an area where the third lens module is located, 
 the third lens module converges the light wave that passes through the second lens module to display the input image plane in a space adjacent to the third lens module, and 
 a focal power of the second lens module is the same as a sum of a focal power of the first lens module and a focal power of the third lens module. 
 
     
     
       13. The apparatus of  claim 12 , wherein
 the first lens module is placed in contact with the spatial light modulator, and 
 further comprises a spatial filter disposed in parallel with the second lens module, and spatially blocks optical noise including a DC component, a conjugate component, or a high-order component of the modulated light wave, 
 a sum of a size of the second lens module and a size of the spatial filter is the same as a size of the first lens module, and 
 the third lens module converges a signal of the modulated light wave where the optical noise is removed. 
 
     
     
       14. The apparatus of  claim 13 , wherein
 an entire region of the spatial light modulator includes a plurality of pixel blocks including a plurality of pixels, 
 the first lens module is disposed in parallel corresponding to each of the pixel blocks and includes a plurality of first lenses for applying focusing power to the light waves modulated in each of the pixel blocks, 
 the second lens module is disposed in parallel corresponding to each of the pixel blocks and includes a plurality of second lenses for projecting the light waves modulated in each of the pixel blocks to an area where the third lens module is located, and 
 the third lens module is disposed in parallel corresponding to each of the pixel blocks and includes a plurality of third lenses for converging the light waves transmitted by each of the second lenses. 
 
     
     
       15. The apparatus of  claim 14 , wherein
 a size of each of the first lenses, a size of each of the second lenses, and a size of each of the third lenses is equal to the size of each of the pixel blocks, and 
 a focal length of each of the first lenses is equal to a focal length of each of the third lenses. 
 
     
     
       16. The apparatus of  claim 15 , wherein
 each of the first lenses consists of a DOE (diffractive optical element) including a holographic optical element (HOE), and 
 each of the first lenses includes the DOE or HOE of a volume-type diffractive optical element structure and reduces intensity of light waves of a higher-order term propagated to a region where other adjacent pixel blocks and other first lenses corresponding to the other adjacent pixel blocks are located. 
 
     
     
       17. The apparatus of  claim 16 , wherein each of the second lenses includes a DOE (diffractive optical element) including a holographic optical element (HOE), and blocks a direct current (DC) component, a phase-conjugate component of a predetermined hologram signal, and a high-order component among the modulated light waves using an angular selective characteristic of the HOE. 
     
     
       18. The apparatus of  claim 17 , further comprising a plurality of partition walls for blocking propagation of the modulated light waves in one pixel block of the spatial light modulator to an area where other adjacent pixel blocks and a first lens to a third lens corresponding to the other adjacent pixel blocks is located. 
     
     
       19. The apparatus of  claim 18 , wherein
 the spatial filter includes a single sideband filter, and 
 the single sideband filter removes optical noise by phase-shifting for the light waves modulated by the spatial light modulator. 
 
     
     
       20. A hologram displaying apparatus, comprising:
 a light source configured to emit light; 
 a spatial light modulator including a plurality of pixels configured to diffract the emitted light; 
 a first lens in contact with a pixel block including some pixels of the plurality of pixels of the spatial light modulator and configured to focus the light diffracted by the pixel block; 
 a second lens configured to transmit remaining diffracted light of the focused diffracted light except a noise component; 
 a spatial filter disposed in parallel with the second lens and configured to block the noise component of the focused diffracted light; and 
 a third lens configured to display a hologram by focusing light waves of which the noise component is removed, 
 wherein both of the second lens and the spatial filter are disposed on a back focal plane of the first lens.